Geology of the Beach:
The yellow brown sandstones that contain the fossils are part of the Purisma formation. Collecting is best at low tide, when the outcroppings are most exposed. 
Paleontology of the Fossils:
The fossils originate from the Pliocene epoch of the Neogene period. Bivalves, gastropods, sea urchins, crabs, marine mammal bones from whales and seals can be found. Shark teeth have also been recovered from the beach, but are rare.
An extensive photo gallery of the fossils common at Capitola Beach can be found here: http://nextcenturyimages.com/nature/capitolafossils2307/index.html
Works Cited:
“CA Capitola,” (Paleontica Fossiel August 2012) <http://english.fossiel.net/sites/fossil_site.php?plaats=506>
California Fossil Sites 